Synchronizing system



June 25,1929. w, MEYER 1,718,477

' 'syucrmonxzme SYSTEM Filed Jan. 23, 1925 4 Sheets-Sheet l Fig.1.

lnyentor FriedmchW Meger,

His Attorneg.

June 25, 1929. I F. w. MEYER 1.718.477

SYNCHRONIZINQ SYSTEM filed Jan. 23, 1925 4 Sheets-Sheet 2 Fig. 5.

.0 Inventor a Fr iedrichw. Meger,

His Attorneg.

' n /WA/Vm June 25, 1929. F, w, MEYER 1,718,477

swcnnomzm'i SYSTEM Filed Jan. 23, 1925. 4 Sheets-Sheet s lnyentor: Ffledrlchw Meger,

His Attorneg- June 25, 1929.

F. W. MEYER SYNCHRONIZING SYSTEM 4 Sheets-Sheet 4 Filed Jan. 23, 1925 I II n ml Ww wwfm th m n .w t e r A vd M w W H .H .b

Patented June 25, 1929.

UNITED STATES PATENT OFFICE.

FRIEDRICH WILHELM MEYER, OF BRAUNSCHWEIG, GERMANY, ASSIGNOR TO GEI\T ERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

SYNCHRONIZING SYSTEM.

Application filed. January 23, 1925.

My invention relates to synchronizing systems, and has for its object the provision of an improved synchronizing system which 1s -apable of being operated automatically both to cause a predetermined relation to be established between the electrical conditions of two alternating current systems or sources and to cause these systems or sources to be interconnected when such a relation has been established. A further object of my invention is the provision of an improved means for producing an effect which is dependent 011 the resultant frequency of two alternating current systems.

In my Letters Patent of the United States, No. 1,592,611 granted July 13, 1926, I haye disclosed a synchronizing system wherein electron discharge devices are utilized to produce interconnection of two alternating current systems when the proper relations have been established between their electrical conditions. My present invention is in some respects similar to that disclosed by my aforesaid application but differs therefrom in that it comprises an improved means for producing an effect dependent upon the resultant frequency of the two systems and is arranged to cause a condition of synchronism to be established between these lines.

My invention will be better understood from the following description when considercd in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Referring to the drawings, Fig. 1 shows a synchronizing system wherein an electron discharge device is utilized in connection with tachometer machines for producing an effect proportional to the resultant frequency of two alternating current systems; Figs. 2, 3, 4- and 5 show different apparatus which may be utilized in connection with an electron discharge deviceto produce an effect dependent on the resultant frequency of the alternating current systems; Fig. 6 illustrates certain features of the apparatus shown in Fig. 5; Fig. 7 shows a synchronizing system wherein apparatus similar to that of Fig. 5 is utilized to produce an effect dependent upon the resultant frequency of the two systems; and Fig. 8 shows an apparatus which is in many respects similar to that of Fig. 5.

Fig. 1 shows two alternatiirig current sys- Serial No. 4,351.

tems 1 and 2 which are arranged to be interconnected through a switch 3 provided with operating coils 4 to 9 inclusive for causing the systems 1 and 2 to be interconnected when their electrical conditions are substantially the same or, in other words, when they are in phase and operating substantially at the same voltage and frequency. As hereinafter explained in greater detail, the energization of coils 4 and 5 is controlled through electron discharge devices 10 and 11 which are arranged to produce an effect dependent on the phase relation existing between the two systems; energization of the coils 6 and 7 is controlled through electron discharge devices 12 and 13 which are arranged to produce an effect dependent on the resultant voltage of the two systems; and energization of the coils 8 and 9 is controlled through an electron discharge device 14 and tachometer machines 15 and 16 which are arranged to produce an effect dependent on the difference between the frequencies of the systems.

The discharge device 10 is shown as a vessel comprising two compartments 0r chambers in one of which are located anodes 17 and cathode l8 and in the other of which are located anodes 19 and cathode 20. The anodes 17 and 19 are arranged to be connected to the alternating current systems 1 and 2 respectively through transformers 21 and 22, the secondary windings of the transformer 21 being arranged to have its midpoint connected to the cathode 18 through reactor 23 and resistor 24 and the secondary winding of the transformer 22 being likewise arranged to have its midpoint connected to the cathode through reactor and resistor 26. With these connections, the rectified voltage of systems 1 will be impressed on reactor 23 and resistor 24; the rectified voltage of system 2 will be impressed on reactor 25 and resistor 26; and by interconnecting the left hand ends of the resistors 24 and 26, there may be produced between the right hand ends of these re sistors a difference in potential which is dependent on the sum of the rectified voltages of the systems 1 and 2.

The electron discharge device 11 comprises a bipartite vessel in one chamber of which are located an anode 27, grid 28 and cathode 29 and in the other chamber of which are located anode 30, grid 31. and cathode 3.;

The cathode 29 is interconnected with the grid 28 through resistors 24 and 26, a sec ondary circuit of a transformer 33 which has its primary winding connected to the line 2',and a secondary winding 36 of-a transformer 34 which has its primary winding connected to the line. The cathode 32 is likewise interconnected with the grid 31 through resistors 24 and 26, secondary circuit 37 of the transformer 33 and secondary circuit 38 of the transformer 34.

It will be observed also that the operating coil 4 of the switch 3 is connected between cathode 29 and anode 27 through a current source 39 and that the operating coil 5 is likewise connected between the cathode 32 and anode 30 through a source 40. With these connections, the difference between the sum of the system voltages and the sum of the rectified system voltages is impressed on the grid circuits of the electron discharge device 11; the energization of switch operating coils 4 and 5 is a minimum when the sy tems are in phase and closure of the switch 3 is always-favored when the systems are in phase regardless of whether the system voltages are exactly equal or differ somewhat in value.

The electron discharge device 12 comprises anodes 41 arranged to be connected to the system 1 through a transformer 42, anodes 43, which are connected to the system 2 through transformer 44, and a cathode 45. A resistor 46 is connected between the midpoints of the secondary windings of the transformers 42 and 44 and is arranged to have its midpoint connected to the cathode 45 through a reactor 47 which is provided for smoothing outpulsations in the current transmitted through the resistor 46. With these connections, the resultant difference of the rectified system voltages is impressed on the resistor 46.

The electron discharge device 13 comprises two chambers, one of which contains an anode 48, a grid 49 and a cathode 50 and the other of which contains an anode 51, grid and cathode The operating coil 6 of the switch 3 is connected between the anode '48 and the cathode 50 through a source of direct current 54. The operating coil 7 is connected between the cathode 53 and the anode 51 through a current source 55. The grid 49 is connected to the cathode 50 through the resistor 46 in one direction while the grid 52 is connected to the cathode 53 through the resistor 46 in the reverse direction. l Vith these connections, the resultant difference of the rectified system voltage is impressed on the resistor 46; this resultant voltage is impressed on the circuits of grids 49 and 52 in opposite directions; energization of the switch operating coils 6- and 7 is reduced to a minimum when the voltages of the two systems are equal; and closure of the switch is favored when the system voltages have the same value.

In so far as described up to this point, the apparatus of Fig. l is responsive to the relations existing between the electrical conditions of the two systems but is incapable of exerting any influence upon these relations. It is sometimes desirable that the synchronizing apparatus be arranged to cause a condition of synchronism to be established automatically between the two systems. If it is desired automatically to synchronize the system 1 with the system 2, for example, it is necessary that electroresponsive means be provided for controlling the voltage and frequency of the machine from which current is supplied to the system 1. This may be done in a number of ways.

In Fig. l the system 1 is shown as arranged to be supplied with current from an alternator 56 which is mecl'ianically coupled to a prime mover shown as a direct current motor 57. The alternator 56 is provided with field windings 58, 59, 60 and 61 and with slip rings 62 through which its armature winding is connected to the system 1. Gurrent is supplied to the field winding 58 from a suitable source through the busses 63 and 64 and to the field winding 59 from this source through bus 63, conductors 65 and 66, adjustable resistor 67, conductor 63 and bus 64. Electroresponsive means, shown as pilot motor 69 of the double commutator type, is arranged to have one of its com-- mutators connected between the anode 48 and cathode 50 in parallel 'ith' the switch operating coil 6 for controlling the current of the alternator field 59 in accordance with the resultant voltage difference of the systems l and 2. The other armature of this motor is connected between the cathode and the anode 51 in parallel with the switch operating coil 7. \Vith these connections, the current of the field winding 59, and consequently the voltage of the alternator 56, will be increased at a comparatively high rate when the resultant voltage difference is large and at a comparatively low rate when the resultant voltage difference is low. This method of operation is of great advantage in that there is a gradual decr ase in the rate of voltage change as the voltage of system 1 approaches that of system 2. This decrease in the rate of voltage change is further accentuated by the field windings 60 and 61 which are connected to the electron discharge device 13 in parallel with the switch operating coils 6 and 7 respectively. It should be noted, however, that the influence of the windings 60 and 61 can be utilized to advantage only when the systems are operating in the neighborhood of synchronism for the reason that the change in alternator excitation occasioned lit) by equalization of the power system voltages may unfavorably effect the power factor at which the systems operate after they have been interconnected. The windings 60 and 61 should therefore not be energized until sometime after operation of the generator is initiated. With proper design of the wind ings 60 and 61, it has been found that there is no tendency for the voltage of the system 1 to become larger than that of system 2 and that the power factor may be maintained without difficulty.

The switch operating coils 8 and 9 are arranged to be energized through the tachometer machines 15 and 16 and the electron discharge device 14 in accordance with the resultant frequency of the systems 1 and a. The tachometer machine 16 arranged to be driven by a synchronous motor at a speed dependent on the frequency of the system 2. The tachometer machine 15 is coupled to the alternator 56 by which it is driven at a speed proportional to the frequency of the system 1. 'The machines 15 and 16 are interconnected to impress the resultant difference of their generated voltages upon the circuits of the grids 71 and 72 of the device 14 which comprises a bipartite vessel in one chamber of which are located the grid 71, an anode 73 and a cathode 74, and in the other chamber of which are located the grid 72, anode and cathode 76. It will be observed that the operating coil 8 is connected between the anode 73 and cathode 74 through a current source 76 while the operating coil 9 is connected bet-ween anode 75 and cathode 76 through a current source 77.

Assuming the machines 15 and 16 to have exactly the same characteristics, the potentials of the grids 71 and 72 will decrease as the frequency of the system 1 approaches that of the system 2 the energization of the operating coils 8 and 9 will be decreased in proportion to' the decreases in the potentials of the grids 71 and 72; and closure of the switch 3 will be favored when the frequencies of the two systems are substantially equal.

The motor 57 is shown as provided with a plurality of field windings 78, 79, and 81. The field winding 78 is arranged to be supplied with current from a suitable source through the busses 63 and 64. The winding 79 is arranged to be supplied with current through bus 64, adjustable resistor 82, and bus 63. Electroresponsive means, shown as a pilot motor 83 of the double armature type, is provided for operating the resistor 82 in accordance with the resultant frequency of the systems 1 and 2 and measured by the resultant difference between the voltages of the machines 15 and 16. When this resultant voltage difference is high, the resistor 82 is operated by the motor 83 to change the current of the field winding 79 and increase the speed of the motor 57 at a comparatively high rate. As the value of the resultant voltage difference becomes less, the rate at which the speed of the motor 57 increases gradually decreases; the rate of increase in the frequency of the alternator 56 becomes lower and lower and the tendency of the frequency of the alternator 56 and system 1 to become greater than that of system 2 is to a large extent obviated. A. further factor in producing this result is the influence exerted on the motor excitation by the field windings'80 and 81 which are connected between anode 7 3 and cathode 74 and between anode 75 and cathode 76 respectively in a manner to have their excitation controlled in accordance with the energization of the device 14. It should be noted that since the strength of the field produced through the motor field windings 80 and 81 varies with the resultant voltage difference produced by the tachometer machines 15 and 16, and becomes zero, when the frequencies become equal, the effect produced through these windings can be utilized to advantage only for obtaining fine degrees of speed regulation and for eliminating sparking at the switch contacts when the connections between power sys tems are altered. F or this reason closure of the switches 80 and 81 should be delayed sometime after initiating operation of the motor 57.

In View of what has been said, the operation of the synchronizing system shown by Fig. 1 will be readily understood without detailed explanation. Assuming the frequency and voltage of the power system'l to be lower than the frequency and voltage of the power system 2, closure of the switch 3 is favoredwhen these two power systems are in phase but is prevented by the coils 6 and 7 which are energized in accordance with the resultant voltage difference of the two power systems, and by the coils S and 9 which are energized in accordance with the resultant frequency difference of these two systems. As the Voltage of the power system 1 is increased due to the increase in excitation of the alternator 56 by operation of the motor 69 and by the field coils 60 and 61 which, as previously explained, should not be energized until the. systems are near synchronism, the energization of the operating coils 6 and 7 will be gradually decreased until the voltages of the two power systems are substantially equal. Under these conditions, the switch operating coils 4, 5, 6 and 7 have their energization reduced to a minimum when the two power systems are in phase but closure of the switch 3 will be prevented due to the fact that the resultant frequency difference of the two systems is high enough to maintain the en ergization of the operating coils 8 and 9 at a comparatively high value. As the frequency of the system 1 is increased due to change in the excitation of the motor 57 by operation of the motor 83 and by direct excited field coils and 81 which as previously explained, should not be energized until the systems are near synchronism, the energization of the coils 8 and 9 will be decreased and will reach a minimum value when the frequencies of the two systems are substantially equal. Under these conditions closure of the switch 3 will be produced when the systems, operating at substantially the same voltage, are brought into phase with one another.

Fig. 2 shows a machine which may be utilized to perform the functions performed by the tachometer machines 15 and 16 of Fig. 1, the field structure 82 of the machine being arranged to be rotated by the synchronous motor 70 and its armature 88 being coupled to the alternator 56. As will be readily understood, the voltage generated by the machine of Fig. 2 will be proportional to the resultant difference in the frequencies of systems 1 and 2 and may be utilized to eon trol the operation of the electron discharge device in' the same manner as the tachometer macnincs 15 and 16 of Fig. 1.

Fig. 3 shows a machine 8 1 which is operable in a well known manner to produce an effect dependent on the resultant difference between the frequencies of polyphase lines 1 and 2, and which may be utilized in connection with the system of Fig. 1 to perform the functions performed by the tachon'ieter machines 15 and 16. The machine 8 1 is a ranged to have its stator windings 85, 86 and 87 direct connected and cross connected between the various conductors of polyphase lines 1 and 2 and to have its rotor winding 88 mounted on a shaft 89 to which are coupled a synchronous generator 90 and the movable member of a rneostat 91 which may be utilized for rough adjustments in the value of the current transmitted through a field winding 78 of motor 57.

It will be observed that the slip rings 93 of the synchronous generator or alternator 90 are connected to the grids 71 and. 72 of the electron discharge device 1 1; that the cathodes 74 and 76 are connected to the midpoint of a resistor 94 which is connected be tween the grids 71 and 72; and that the operating circuits of the device 1 1 are connected in parallel to the commutator of a motor 95 to the switch operating coils 8 and 9. With these connections the motor 95 and the switch operating coils 8 and 9 will be ene gized in accordance with the resultant d'ifrerence between the frequencies of lines 1 and 2. Like the motor 83 of Fig. 1, the

motor 95 will operate to change the excitation of the prime mover 57 at a compare t-ively high rate when the resultant difference between the lines 1 and 2 is large. As this resultant difference decreases in value, however, the rate of change in the value of the prime mover excitation. decreases so that there is little danger of the frequency of line 1 exceeding that of line 2". As in the case of Fig. 1, the switch operating coils 8 and 9 have their energization reduced to a minimum when the frequencies of the two lines are substantially equal. Further details in the arrangement and operation of the apparatus shown by Fig. 3 will be readily understood in view of what has been said in connection with Fig. 1.

here the alternator 56 is driven by a steam turbine, an internal combustion engine or the like, the system of Fig. 1 may be modified as indicated by Fig. 4. This figure shows a direct current generator 96 which is assumed to be driven in accordance with the resultant difference between the frequencies of the lines 1 and 2 as measured or indicated by the tachometer machines 15 and 16 of Fig. 1, the machine of Fig. 2, the machine 84 of Fig. 3,01 by any other suitable means. In this modification of the system the motor 83 is utilized to control the adjustment of a resistor 97 connected to a current source 98 in series with a coil 99 which may be utilized in a well known manner to control the governor 'etting or fuel supply of a steam turbine, internal eombustion engine, or other prime mover. The operation of this modification will lie-readily understood without detailed explanation.

Fig. 5 shows still another arrangement for producing an effect which determined or measured by the resultant difference between the frequencies of the power lines 1 and 2. In this arrangement, the corresponding conductors of the polyphase lines 1 and 2 are interconnected through reactors 100, 101 and 102 respectively. lVith these connections, the resultant difference between the voltages of one phase of the lines 1 and 2 is applied to the reactor 102; the resultant difference between the voltages of another phase of these lines is appliedto the reactor 101; and the resultant difference between the voltages of still another phase of these lines applied to the reactor 100.

Opposite ends of the reactor 102 areconneeted to anodes 103 and 104 of an electron discharge device 105 which is arranged to have its cathode 106 connected to the midpoint of reactor 102 through resistor 107 and reactor 108. An electron discharge device 109 comprising a cathode 110, grid 111 and anode 112 is arranged to have its grid or control circuit connected across a portion of the resistor 107.

The effect of the device 105 and reactor 108 on the line voltage applied to the reactors 100, 101 and 102 are illustrated by, Fig. 6 wherein the part of the curve between the lines aa and bb represent the voltages applied to the reactors; the part of the curve between the lines bb and c-o represent the voltages as rectified by the device and the part of the curve between the lines c-c and (Z(Z show the current pulsations as smoothed out by the reactor 108. The last part of the curve thus shows the character of the voltage applied to the control circuit of the device 109. The frequency of the voltage applied to the control circuit of the device 109 is dependent on the difference between the frequencies of lines 1 and 2 and becomes lower as synchronism between the systems is approached. The terms rectified voltage and rectified current, as used herein, are intended to comprise any voltage having both alternating and direct current components. The term resultant frequency is used to indicate the beat frequency produced by the interaction of the two alternating current systems. This frequency is of course comparatively high when the systers are operating at widely different frequcncies and graduallydecreases as the system frequencies approach equality. It will be observed that the reactor 108 serves as a filter in that it tends to exclude currents of undesirable frequencies from the operating circuit of device 105.

The cathode 110 and anode 112 of the de vice 109 are shown as interconnected through a current source 113, a resistor 114, a reactor 115 and the primary winding 116 of a transformer 117 which is arranged to supply current through its secondary winding 118 to one phase of a motor having its rotor winding 120 arranged to rotate with the shaft 121. The reactor 115 cooperates with the reactor 103 in excluding high frequency currents from the operating circuit of the device 109. The connections between phase windings 122 and 123 of this motor and the reactors 101 and 100 respectively are similar to those between phase winding 119 and reactor 102, but have been omitted from the drawing in order to avoid confusion. Mounted on the shaft together with this motor is a direct current machine which is provided for energizing the coils 8 and 9 and the field wind ing 7 9 of the motor 57 in accordance with the resultant difference between the frequencies of the power lines 1 and 2. The machine may be utilized as the machine 90 of Fig. 3 or as the machine 96 of Fig. 4 but has been shown as arranged to control the energization of coils 8 and-9 and of pilot motor 83.

Assuming that it is desired to bring the line 1 into synchronism with the line 2 and that the frequency of the line 1 is high, it will be readily understood that the frequency of the control or grid voltage of the device 109 will decrease as the frequencies of the lines 1 and 2 approach equality. As a result of this decrease in grid voltage, the frequency of the current supplied to the driving motor of machine 124 will decrease, the speed at which the machine 124 is driven-will correspondingly decrease, and closure of the switch 3 will be favored when the frequencies of lines 1 and 2 are substantially equal due to the fact that the energization of the coils 8 and 9 is at a minimum under these conditions.

Fig. 7 shows a complete synchronizing system which is similar to that of Fig. 1 in some respects, but differs therefrom in that the tachometer machines 15 and 16 are replaced by an electron discl'iarge device 125 which is arranged to produce an effect dependent on the resultant difference between the frequencies of'lines 1 and 2 and in that a somewhat different apparatus is utilized to produce an effect which is dependent upon the phase relation existing between the two systems. Other more or less important distinctions between the systems of Fig. 1 and Fig. 7 will be which follows.

In Fig. 7 the lines 1 and 2 are cross connected through reactors 126 and 127 which are provided for impressing on the operating circuits of the electron discharge device 128 a Voltage which is dependent on the sum of the line voltages and is proportional in value to the resultant frequency of the lines 1 and 2. The device 128 comprises anodes 129 and 130 and a cathode 131 which is connected to the midpoint of reactor 127 through resistor 132 and the primary winding 133 of a transformer 1341. The second ary winding 135 of transformer 134 is connected between the grid 136 and cathode 137 of an electron discharge device 138 through resistors 24- and 26 which, as explained in connection with Fig. 1, are arranged to produce between their right hand ends a voltage drop proportional in value to the sum of the rectified system voltages. The switch operating coil 4 and field winding 139 of motor 57 are connected in parallel between anode 140 and cathode 137 of the device 138, a current source shown a battery 141 pointed out in the description being provided to energize the coil 4 and field winding 139 in accordance with the potential of grid 136.

\Vith these connections, the potential of grid 136 is produced by balancing the rectified system voltages against the instantaneous rectified resultant voltage of the systems which is smoothed out as explained in connection with Fig. 6, the secondary voltage of transformer 134 is comparatively low and the potential of grid 136 is comparatively high when the systems are not in phase; the secondary'voltage .of transformer 134 increases to its maximum value and the potential of grid 136 reaches its minimum value as the systems come into phase, and closure of the switch is favored when the systems are in phase.

The operation of the electron discharge devices 12 and 13 to control the energization of the switch operating coil 6 and of field winding 59 of generator 56 in a manner to raise the generator voltage at a rate which decreases as the system voltages approach equality and to favor closure of the switch 3 when the system voltages are equal will be readily understood in view of what has been said in connection with Fig. 1. It should be noted, however, that the pilot motor 69, through which the generator field rheostat 67 is operated, is provided with a field winding 154 which has its excitation regulated in accordance with the energization of device 13 in a manner to facilitate adjustment of the alternator excitation and voltage, when the systems are operating in the nei hborhood of s nchronism.

In the system of Fig. 7, operation of the electron discharge device 14 is controlled through a device 125 and reactors 142 and 143 which are direct connected between the corresponding conductors of the power systems 1 and 2. It will he observed that the reactor 142 is arranged to have its opposite terminals connected to the anodes 144 and 145 of device 125 and to have its midpoint connected to the cathode 146 of this device through resistor 147 and primary winding 148 of a transformer 149; that the secondary winding 150 of the transformer 149 has its opposite ends connected to the grids 71 and 72 of device 14 and its midpoint connected to cathodes 74 and 76 of this device through a reactor 151 which is provided for filtering the alternating component current out of the resultant frequency current transmitted through the device 14; and that a current source shown as a battery 152 is provided for energizing the pilot motor 83 and switch operating coil 8 in accordance with the potentials of grids 171 and. 172. As in the system of Fig. 1, the pilot motor 83 is utilized to exert an influence on the excitation, of motor 57 tending to change the frequency of alternator 56 at a rate which diminishes as the system frequencies approach equality. I

tron discharge device 138 and which may be designed to exert an influence tending to accelerate or retard the motor 57 as long the right phase is not attained. The current of the winding of course disappears when the systems come into phase. This winding must be designed with due consideration for its effect on the excitation produced by the other motor field windings and the influence of these windings upon the field winding 139.

The device 125, the resistor 147 and the transformer 149 may be regarded as a combined rectifier and filter through which only rectified resultant frequency currents are supplied to the device 14, the inductance of the transformer 149 serving to filter out currents of frequencies other than the resultantfrequency of the systems and the resistor 147 serving to accentuate somewhat the effect of change in the magnitude of the resultant frequency. The reactor 151 is provided for the purpose of filtering from the grid or control circuits of the device 14 the alternating component of the currents supplied from the secondary winding 150 of the transformer 149. The potentials of grids 71 and 72 are thus substantially constant in value so long as the difference between the frequcncies of systems 1 and 2 does not change. As the frequencies of the systems approach equality, however, the resultant frequency decreases in value; the potentials of the grids 71 and 72 are decreased; the energization of electron discharge device 14 and of the coil 8 are reduced; and closure of the switch 3 is favored when the systems are in synchronism.

The fact that the servoinotors 83 and (39 function to change the alternator frequency and voltage at a rate which decreases as equality in the system frequencies and voltis approached is of advantage in that the danger of passing through synchronism is avoided. As previously indicated, the influence which is exerted on the generator frequency and excitation through the devices 13 and 14 independently of the servomotors 83 and 69 has its .main advantage in producing fine adjustn'ients in the neighborhood of synchronism between the two systems. For this reason, the circuits through which exciting current is supplied directly from the devices 18 and 14 to the motor 57 and alter-- nator 56 should not be closed too early as otherwise heavy circulating currents are likely to be produced between the two sys-' tems due to the fact that no current is transmitted through these devices after closure of switch 3 and to the consequent reduction in the motor and alternator field currents.

It should be noted that the combinations of electron discharge devices and reactors shown by Figs. 5 and 7 have utility wherever it is desired to measure the difference becation of difference between two frequencies.

In Fig. 8 this combination is shown as utilized only to produce an influence dependent on the difference between the frequencies of the systems 1 and 2. This figure shows the lines 1 and 2 as having their corresponding conductors connected together through resistor 155 and primary winding 156 of transformer 157. The secondary winding 158 of the transformer 157 is arranged to have its opposite terminals connected to anodes 159 and 160 of the electron discharge device 161 and to have its midpoint connected to the cathode 162 of this device through a reactor 163 provided for the purpose of filtering currents of undesirable frequencies from the circuit of the device 161 and through a resistor 164: which is provided for producing a potential drop dependent on the resultant frequency of the two systems. As will be readily understood, the current transmitted through resistor 16-1 pulsates in value. In order to eliminate thedirect current component of this pulsating current, a battery 165 is connected'to the opposite terminals of the resistor 164: through a second resistor 166. lVith these connections there is impressed on the leads 167 and resistor 166 an alternating current which is of the same frequency as the resultant frequency of the two systems and which may be utilized to actuate an alternating current meter or to drive a motor at a speed proportional to the difference between the frequency systems, either directly or by means of a special relay as shown in Fig. 5.

If it is desired to produce at the same time a direct current which varies in accordance with the difference between two frequencies and which decreases as the frequencies approach equality, a second electron discharge device 168 provided with anodes 169, 170 and 171, cathodes 172 and 173, and grid 17 6 may be arranged to cause a voltage drop proportional in value to the resultant frequency of the two systems to be produced across a resistor 17 1, a reactor 17 5 being provided to filter the alternating component out of the rectified resultant frequency current transmitted to the device 168. Under these conditions, the potential of grid 17 6 will decrease as the frequencies of the systems approach equality and the direct current transmitted to the device 17 7 from the source 178 will change accordingly. It will be apparent that other modifications of the combinations comprised in the systems of Figs. 5 and 7 will readily occur to those skilled in the art.

The embodiments of the invention illustrated and described herein have been selected for the purpose of clearly setting forth the principles involved. It will be apparent, however, that the invention is susceptible of being modified in many ways to meet the different conditions encountered in its use and I therefore aim to cover by the appended claims all modifications within the true spirit and scope of my invention.

lVhat I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a synchronizing system, two electric power systems, switching means for interconnecting said power systems, electron discharge means connected to said systems so that the output of said electron discharge means varies in accordance with the relation between predetermined electrical conditions of said systems, means controlled by the output of said electron discharge means for controlling the operation of said interconnecting means whereby said systems are interconnected only when a predetermined relation exists-between predetermined electrical conditions of said systems, and regulating means controlled by the output of said elec tron discharge means for varying the electrical conditions of one of said systems in a manner to produce said predetermined relation. V

2. In a synchronizing system, two electric power systems, switching means for interconnecting said power systems, electron discharge means connected to said systems so that the output of said electron discharge means varies in accordance with the relation between predetermined electrical conditions of said systems, means controlled by the output of said electron discharge means for controlling the operation of said interconnecting means whereby said systems are interconnected only when a predetermined relation has been established between the electrical conditions of said systems, and frequency regulating means controlled by the output of said electron discharge means for varying the frequency of one of said systems in a manner to produce said predetermined relation between the electrical conditions of said systems.

3. In a synchronizing system, two electric power systems, switching means for interconnecting said power systems, electron discharge means connected to said systems so that the output of said electron discharge means varies in accordance with the relation between predetermined electrical conditions of said systems, means controlled by the output of said electron discharge means for controlling the operation of said interconnecting means so that said systems are interconnected only when a predetermined relation has been established between the electrical conditions of said systems, and voltage regulating means controlled by the output of said electron discharge means for varying the voltage of one of said systems in a manner to produce said predetermined relation between the electrical conditions of said systems.

i. In a synchronizing system, two electric power systems, switching means for interconnecting said power s3 tems, electron discharge means connected to said systems so that the output of said electron discharge means v .rics in accordance with the relation between prodetermined. electrical conditions of szi d systems, means controlled by the output of said. electron discharge means for controlling the operation of said interconnecting means so that said systems are interconnected only when a predetermined relation exists between predetermined electrical conditions of said systems, and regulating means controlled by the output of said electron discharge means for varying the predetermined. electr' ial condition of one o't said systems at a rate which diminishes as said predetermined relation is approx-relied.

5. In a synchronizing system, two electric power systems, an electric generator for supplying current to one of said power systems, switching means for interconnecting said power systems, electron discharge means connected. to said systems so that the outputs of said electron discharge means vary in accordance with the relation between predetermined electrical conditions of said systems, means controlled by the outputs of said electron discharge means for effecting the operation of said interconnecting means when a predetermined relation exists between. the electrical conditions of said systems, and voltage and frequency regulating means controlled by the outputs of said electron discharge means tor varying the frequency and voltage of said genorator in a manner to produce said predetermined relation.

6. In a synchronizing system, two electric power systems, an electric generator for supplying current to one of said power systems, switching means for interconnecting said power systems, electron discharge means connected to said systems so that the output of said electron discharge means varies in accordance with the relation between predetermined electrical conditions of said systems, means controlled by the outputs of said electron discharge means for effecting the operation, of said interconnecting means when a predetermined relation exists between the electrical conditions of said systems, and voltage and frequency regulating means controlled by the out 3111; of said electron discharge means for changing the frequency and voltage of said generator at a rate which diminishes as said predetermined relation is approached.

7. In a synchronizing system, two electric power systems, an electric generator supplying current to one of said systems, switching means for interconnecting said power systems, electron discharge means connected to said systems so that the output or said electron discharge means varies in accordance with the relation between predetermined electrical conditions of said systems, means controlled by the output of said electron discharge means for :ausing the op eration of said interconnecting means when systems, electron discharge means connected to said systems so that the output of said electron discharge means varies in accordance with the .relation between predetermined electrical conditions of said systems, means controlled by the output of said. electron discharge means for causing the operation of said interconnecting means to interconnect said systems when a predetermined relat-ion has been established between the electrical conditions of said systems and regulating means controlled by the output of said electron discharge means for varying the speed of said prime mover in a manner to produce said predetermined relation.

9. In a synchronizing system, two electric power systems, an electric generator for supplying current to one of said systems, a prime mover for driving said generator, switching means interconnecting said power system, electron discharge means connected to said systems so that the output of said electron discharge means varies in accordance with the relation between predetermined electrical conditions of said systems, means controlled by the output of said. electron discharge means for eiiecting the operation of said interconnecting means to interconnect said systems when a predetermined relation has been established between the electrical conditions of said systems, elec troresponsive means controlled by the output of said electron discharge means and regulating means controlled by said electroresponsive means for changing the speed of said prime mover at a rate which diminishes as said predetermined relation is approached.

10. A synchronizing system wherem means are arranged to interconnect two electric power systems one of which is supplied with current from an electric generator and wherein electron discharge means are provided for causing said interconnecting means to be ope 'atcd when a predetermined relation has been established between the electrical conditions of said systems, comprising electroresponsive means oper able in accordance with the energization of said electron discharge means for changing the excitation of said generator at a rate which diminishes as said relation is approached, and a generator field winding connected directly to said electron discharge lneans for producing fine adjustments in the voltage of said generator when said systems are operating in the neighborhood of synchronism.

11. A synchronizing system wherein means are arranged to interconnect two electric power systems one of which is supplied with current from an electric generator driven by an electric motor and wherein electron discharge means are provided for causing said interconnecting means to be operated when a predetermined relation has been established between the electrical conditions of said systems, comprising electroresponsive means operable in accordance with the energization of said electron discharge means for changing the speed of said motor at a rate which diminishes as said relation is approached and a motor field winding connected directly to said electron discharge means for producing fine ad ustments in the speed of said motor.

12. In a synchronizing system, two electric power systems, an electric generator for supplying current to one of said systems, a prime mover for driving said generator, switching means for interconnecting said power systems, electron discharge means connected to said systems so that the output of said discharge means varies in accordance with the difference between the frequencies of said systems, and means responsive to the output of said electron discharge means for controlling the speed of said prime mover.

13. In a synchronizing system, two electric systems, means adapted to rectify the resultant frequency current of said systems, an electron discharge device and a control circuit therefor, a circuit arranged to transmit said current to the control circuit of said device and means for excluding currents of undesirable frequencies from said control circuit.

14. In a synchronizing system, two electric systems, a device adapted to be operated in accordance with the difference between the frequencies of said systems, means for rectifying the resultant voltage of said systems, electron discharge means, and a control circuit therefor, means arranged to be energized in accordance with the frequency of said rectified voltage for controlling the potential of said control circuit, means for filtering currents of undesirable frequenc from said control circuit and an operating circuit arranged to interconnect said i vice and said electron discharge charge means with one of said reactors through said resistor and the primary circuit of said transformer, a second electron discharge means, a circuit interconnecting the secondary circuit of said transformer and said second electron discharge means for controlling the operation of said second electron discharge means, and means connectcd in said control circuit for excluding therefrom currents of frequencies in excess of the frequency of said resultant voltage.

16. In combination, two electric systems, means for producing a potential drop proportienal in value to the sum of the rectified system voltages, means for rectifying the -resultant voltage of said systems, an electron discharge device, and a circuit arranged to be energized in accordance with the difference between said potential drop and said rectified voltage for controlling the operating current of said device.

17. In a synchronizing system, two alternating current systems, means adapted to be connected by the said systems, for transmitting current at the resultant frequency of said systems, means for rectifying said current and an operating circuit for said rectifying means, means for filtering from said operating circuit currents of frequencies other than the resultant frequency of said systems, an electron discharge device and a control circuit therefor, means for transmitting the current rectified by said rectifying means to said control circuit, and means for filtering from said control circuit the alternating component of said rectified current.

18. The method of producing an effect dependent on the difference between the frequencies of two alternating current systems which are interconnected through means for transmitting current at the resultant frequency of said systems which consists in filtering out currents of frequencies other than the resultant frequency of said systems, rectifying said resultant frequency current, and filtering the alternating component from said rectified current.

19. In a synchronizing system, two alternating current circuits, neans for connecting said circuits together, an electron discharge device, a control circuit for said device arranged to be energized in response to predetermined electrical conditions of said circuits, and means controlled by the output of said electron discharge device for oft'ecting the operation of said connecting means when a predetermined relation occurs between said predetermined electrical conditions and for changing the electrical conditions of one oi said circuits to produce said predetermined relation.

20. In a synchronizing system, two alternatin current circuits, means for connecting said circuits together, an electron discharge device, a control circuit for said device arranged to be energized in response to predetermined electrical conditions of said circuits, means controlled by the output of said electron discharge device for effecting the operation of said connecting means when a predetermined relation occurs between said predetermined electrical conditions, electroresponsive means arranged to effect a change in the electrical conditions of one of said circuits, and energizing means for said electroresponsive means controlled by said electron discharge device at a rate which diminishes as said predetern'iined re lation is approached.

21. In a synchronizing system, t-Wo alternating current circuits, means for connecting said circuits together, an electron discharge device, a control circuit for said device arranged to be energized in response to predetermined electrical conditions of said circuits, means controlled by the out-gut of said electron discharge device for e'liecting the operation of said connecting means when a predetermined relation occurs between said predetermined electrical conditions, electroresponsive means arranged to effect a change in the frequency and voltage of one of said circuits, and energizing means for said electroresponsive means controlled by said electron discharge device in a manner to produce said predetern'iined relation between the electrical conditions of said circuits.

In witness whereof, I have hereunto my hand this 16th day of January, 1925.

Dr. FRIEDRICH WILHELM MEYER. 

